Negative emotions such as anxiety, fear, and sorrow are known to be factors that elevate the blood glucose level (1). Conversely, positive emotions such as laughter have been reported to modify the levels of neuroendocrine factors involved in negative emotions (2,3) and to modulate immune function (3,4). However, there have been no studies on the effects of laughter on blood glucose level. The purpose of this study was to clarify changes in the blood glucose level after laughing episodes in patients with diabetes.

A 2-day experiment was performed in 19 patients with type 2 diabetes not receiving insulin therapy (16 men and 3 women, age 63.4 ± 1.3 years, BMI 23.5 ± 0.7 kg/m2, HbA1c, 7.2 ± 0.1% [means ± SE]) and 5 healthy subjects (2 men and 3 women, age 53.6 ± 3.5 years, BMI 24.3 ± 1.6 kg/m2, HbA1c 4.8 ± 0.1% [means ± SE]). On both experimental days, they consumed the same 500-kcal meal (79.9 g carbohydrate, 21.0 g protein, 7.8 g fat, and 1.0 g fiber). On the first day, they attended a monotonous lecture (40 min) without humorous content. On the second day, as part of an audience of 1,000 people attending MANZAI (a Japanese cross-talk comedy) (40 min) in a civic hall, the subjects laughed. Blood glucose was measured from the fingertip by enzyme colorimetric assay using a blood glucose self-measurement apparatus. The subjects estimated their laughter level on a scale of 0–5, and most of them considered that they laughed well (level 4 or 5). Self-monitoring of blood glucose was performed before food intake (fasting blood glucose [FBG]) and 2 h after the meal was started (2-h postprandial blood glucose [PPBG]).

The results are presented as means ± SE. In the patients, the mean 2-h PPBG was 6.8 ± 0.7 mmol/l higher than the FBG after the lecture and 4.3 ± 0.8 mmol/l higher after the comedy show. The difference in the mean increase between the lecture and comedy show was 2.5 ± 0.7 mmol/l (P < 0.005). In the healthy subjects, the mean increases were 2.0 ± 0.7 and 1.2 ± 0.4 mmol/l after the lecture and comedy show, respectively, and the difference was 0.8 ± 0.5 mmol/l (P = 0.138).

These results suggest a significant suppression of the increase in 2-h PPBG by comedy show in patients with diabetes, suggesting that laughter ameliorates the postprandial glucose excursion in the presence of insufficient insulin action. This favorable effect of laughter may include the acceleration of glucose utilization by the muscle motion during the comedy show. However, it is possible that positive emotions such as laughter acted on the neuroendocrine system and suppressed the elevation of blood glucose level.

In conclusion, the present study elucidates the inhibitory effect of laughter on the increase in PPBG and suggests the importance of daily opportunities for laughter in patients with diabetes.